1. Field of the Invention
The present invention relates to a semiconductor device and a fabrication method thereof, more specifically, to a metal-oxide-semiconductor (MOS) transistor and a method for fabricating the same.
2. Description of the Related Art
Advance in the integration of a semiconductor device results in decreasing the size of MOS transistors constituting integrated circuits. Conventionally, a dimension of a gate electrode and a transistor channel length are determined by a photolithography technique for patterning the gate electrode, yet the resolvability of the photolithography technique reaches certain limits, due to limitations of the photolithography equipment and materials. A variety of complementary measures, using an anti-reflection layer, deep ultraviolet (DUV) light, immersion technology, etc., have been developed to overcome the limits of photolithography process, yet still there are limits to fabrication of an ultra-miniaturized, e.g., nano-scale gate electrode. Currently, the widely used light source of KrF has been evaluated to be applicable up to 100 nm technology. However, this light source has limitations on application to 60 nm˜20 nm technologies.